forked from Minki/linux
6ed70a792a
... not kstop_machine. Add a note that irqs are disabled. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
104 lines
2.4 KiB
C
104 lines
2.4 KiB
C
/*
|
|
* Dynamic function tracing support.
|
|
*
|
|
* Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
|
|
*
|
|
* For licencing details, see COPYING.
|
|
*
|
|
* Defines low-level handling of mcount calls when the kernel
|
|
* is compiled with the -pg flag. When using dynamic ftrace, the
|
|
* mcount call-sites get patched lazily with NOP till they are
|
|
* enabled. All code mutation routines here take effect atomically.
|
|
*/
|
|
|
|
#include <linux/ftrace.h>
|
|
|
|
#include <asm/cacheflush.h>
|
|
#include <asm/ftrace.h>
|
|
|
|
#define PC_OFFSET 8
|
|
#define BL_OPCODE 0xeb000000
|
|
#define BL_OFFSET_MASK 0x00ffffff
|
|
|
|
static unsigned long bl_insn;
|
|
static const unsigned long NOP = 0xe1a00000; /* mov r0, r0 */
|
|
|
|
unsigned char *ftrace_nop_replace(void)
|
|
{
|
|
return (char *)&NOP;
|
|
}
|
|
|
|
/* construct a branch (BL) instruction to addr */
|
|
unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr)
|
|
{
|
|
long offset;
|
|
|
|
offset = (long)addr - (long)(pc + PC_OFFSET);
|
|
if (unlikely(offset < -33554432 || offset > 33554428)) {
|
|
/* Can't generate branches that far (from ARM ARM). Ftrace
|
|
* doesn't generate branches outside of kernel text.
|
|
*/
|
|
WARN_ON_ONCE(1);
|
|
return NULL;
|
|
}
|
|
offset = (offset >> 2) & BL_OFFSET_MASK;
|
|
bl_insn = BL_OPCODE | offset;
|
|
return (unsigned char *)&bl_insn;
|
|
}
|
|
|
|
int ftrace_modify_code(unsigned long pc, unsigned char *old_code,
|
|
unsigned char *new_code)
|
|
{
|
|
unsigned long err = 0, replaced = 0, old, new;
|
|
|
|
old = *(unsigned long *)old_code;
|
|
new = *(unsigned long *)new_code;
|
|
|
|
__asm__ __volatile__ (
|
|
"1: ldr %1, [%2] \n"
|
|
" cmp %1, %4 \n"
|
|
"2: streq %3, [%2] \n"
|
|
" cmpne %1, %3 \n"
|
|
" movne %0, #2 \n"
|
|
"3:\n"
|
|
|
|
".section .fixup, \"ax\"\n"
|
|
"4: mov %0, #1 \n"
|
|
" b 3b \n"
|
|
".previous\n"
|
|
|
|
".section __ex_table, \"a\"\n"
|
|
" .long 1b, 4b \n"
|
|
" .long 2b, 4b \n"
|
|
".previous\n"
|
|
|
|
: "=r"(err), "=r"(replaced)
|
|
: "r"(pc), "r"(new), "r"(old), "0"(err), "1"(replaced)
|
|
: "memory");
|
|
|
|
if (!err && (replaced == old))
|
|
flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
|
|
|
|
return err;
|
|
}
|
|
|
|
int ftrace_update_ftrace_func(ftrace_func_t func)
|
|
{
|
|
int ret;
|
|
unsigned long pc, old;
|
|
unsigned char *new;
|
|
|
|
pc = (unsigned long)&ftrace_call;
|
|
memcpy(&old, &ftrace_call, MCOUNT_INSN_SIZE);
|
|
new = ftrace_call_replace(pc, (unsigned long)func);
|
|
ret = ftrace_modify_code(pc, (unsigned char *)&old, new);
|
|
return ret;
|
|
}
|
|
|
|
/* run from ftrace_init with irqs disabled */
|
|
int __init ftrace_dyn_arch_init(void *data)
|
|
{
|
|
ftrace_mcount_set(data);
|
|
return 0;
|
|
}
|